1. Field of the Invention
The present invention relates in general to a device for forming thousands of incisions on the skin for dermal administration of a pharmaceutically acceptable composition liquid or gel medicine, and more particularly, to a device for perforating the skin by rolling a needle assembly, having a plurality of needles, and thereby letting the liquid or gel medicine deeply infiltrate into the skin through the incisions when applying the medicine to the perforated skin.
2. Description of the Prior Art
Insulin is noted to be an efficacious medicine for, in particular, diabetics. However, insulin is a macro molecule having a molecular weight not less than 6000 so that the insulin scarcely infiltrates through the epidermis even when changing the skin characteristics using a chemical solvent. In addition, since insulin, a peptide, is a hydrophilic molecule, it does not have good affinity for the hydrophobic epidermis. In this regard, it has been noted that the insulin by itself cannot penetrate the epidermis and that the skin should be additionally treated when administering the insulin through the skin.
Human skin comprises an outer layer or the epidermis and an inner layer or the endodermis. The epidermis, comprises 20% fat and 40% protein and has a thickness not less than 0.1 mm. Thus, the epidermis barely allows the medicine to infiltrate.
The epidermis comprises protein segments surrounded by fat so that the epidermis has a hydrophobic property. In comparison with the epidermis and the endodermis, both having a water content of at least 70%, the epidermis has a relatively lower water content of about 40%. With the lower water content, the epidermis has a high electric resistance and functions as a protector for protecting the endodermis from outside stimulation such as thermal stimulation.
In the prior art, dermal administration of insulin is generally classified into three types, that is, an ointment type administration, a patch type administration and a spray type administration. Of the above three types, the patch type dermal administration of insulin has been recently studied with much interest.
Korean Patent Publication No. 92-2264 discloses an example of a patch type instrument for dermal administration of insulin. As shown in FIG. 1, the patch type instrument has an insulin solvent reservoir 1 and a high molecular carrier 2. The carrier 2 is evenly applied with insulin powder and has a water-swelling property. The above instrument also has a skin needle carrier 3 which will be swollen by the insulin solvent discharged from the reservoir 1 after attaching the instrument to the skin. A plurality of needles 4 are in a fixed, vertical arrangement in the carrier 3 and will come into contact with the skin when attaching the instrument to the skin. The instrument further includes an electrode 5 for sending current to the reservoir 1 and to the skin, the electrode 5 being arranged in the top section of the reservoir 1.
When using the above patch type instrument for dermal administration, the instrument is attached to the skin such that the needles 4 of the needle carrier 3 come into contact with the skin and form incisions in the epidermis. In this case, the perforations, or the insulin passages which are formed in the epidermis by the needles 4, are temporarily closed due to swelling of the skin. When the electrode 5 is applied with current, DC or ripple current, the ionized insulin and the solvent move to the opposed electrode. At this time, the hydrophilic protein and the polypeptides of the skin are arranged in parallel toward the anode and shrink so that the incisions in the epidermis open. Therefore, the insulin passes the epidermis through the incisions and, thereafter, infiltrates through the endodermis to be transferred to the capillary vessels.
In the above instrument, use of the needles 4 is for perforating only the epidermis having a thickness not less than 0.1 mm and letting the insulin be easily transferred to the capillary vessels through the epidermis, the epidermis and the endodermis and thereby increasing the medicating amount of the delivered insulin.
The above instrument has tens or hundreds of needles fixedly held by the water swelling carrier, the carrier being swollen by the insulin solvent discharged from the reservoir. However, it is very difficult to produce 50-400 .mu.m diameter needles. In addition, as the carrier should be swollen by the insulin solvent discharged from the reservoir, the carrier made of water-swelling material increases the cost.
As the needle carrier and the insulin solvent reservoir are assembled into a set, the instrument should be discarded after one use. The instrument is thus wasteful of material and expensive.
Another problem of the above instrument resides in that the instrument merely has tons or hundreds of needles even though the instrument needs to be provided with thousands of needles for more rapid administration of insulin. Due to the shortage of needles, the amount of insulin solvent transferred to the capillary vessels through the skin for a unit time is insufficient so that diabetics must attache the instrument to the skin for a long time, enduring pain caused by needle perforation and discomfort from the uncomfortable motion caused by the instrument attached to the skin.